1. Field of the Invention
The present invention relates to production of dielectric ceramic material powders and, more particularly, to a method for producing powder of dielectric ceramic materials with a complex perovskite crystal structure.
2. Description of the Prior Art
For production of powder of dielectric ceramic materials composed of a main component consisting of Ba(Ti.sub.1-x-y Zr.sub.x Hf.sub.y)O.sub.3, where 0.05.ltoreq.x.ltoreq.0.25 and 0.ltoreq.y.ltoreq.0.05), and additives including at least one of Ca and Mg, at least one rare earth element, and Mn, a powder method has generally been used comprising the steps of weighing out and mixing powders of carbonates and/or oxides of all the metal elements constituting dielectric ceramics, such as, for example, barium carbonate, titanium oxide, zirconium oxide, hafnium oxide, calcium carbonate, magnesium carbonate, lanthanum oxide and manganese carbonate, grinding the resultant mixture by the wet-process, dehydrating and drying the ground mixture, calcining the dried powder at a high temperature of 1200.degree. C. and above, and mechanically grinding the resultant clinker to prepare powder of dielectric ceramic materials.
However, the above method includes the following problems awaiting a solution. Firstly, it is impossible with the above method to homogeneously mix these constituents of dielectric ceramics with one another at the molecular levels since the constituents are mixed in the powder form of carbonates or oxides. In other words, it is impossible to obtain microscopically homogeneous powder of dielectric ceramic materials. For this reason, when producing dielectric ceramic products with powder of the dielectric ceramic materials of the prior art, it is necessary to fire green products at temperatures of 1300.degree. C. and above.
In addition, the dielectric ceramic material powder has been prepared by calcination at high temperatures of more than 1200.degree. C., resulting in aggregation of particles of the dielectric ceramic material. As a result, it is necessary to crush the calcined powder with a grinding machine having a large shearing force, resulting in introduction of impurities produced by wear of grinding media or inner walls of the grinding machine.